1. Field of the Invention
The present invention generally relates to a UV light irradiating apparatus or a method for irradiating a semiconductor substrate.
2. Description of the Related Art
Traditionally, UV processing apparatuses have been used in the reforming of various processing targets using ultraviolet light or in the production of substances through processes that utilize photochemical reactions. The trend of increasingly integrated devices in recent years has created needs for refined wiring designs and multi-layer wiring structures, which has made it vital to reduce inter-layer volumes to increase the processing speeds of devices while reducing their power consumptions. Low-k (low-dielectric-constant film) materials are used to reduce inter-layer volumes. However, reducing the dielectric constant of a material also reduces its mechanical strength (elastic modulus, or EM), which makes it difficult for the low-k material to withstand the stresses received in subsequent processes such as CMP, wire bonding and packaging. One method to address the aforementioned problem is to cure the low-k material with UV irradiation to improve its mechanical strength (examples are found in U.S. Pat. No. 6,759,098 and U.S. Pat. No. 6,296,909). UV irradiation causes the low-k material to shrink and harden, thereby increasing its mechanical strength (EM) by 50 to 200%. Separately, optical CVD based on photochemical reaction has been studied for years as a way to respond to another demand stemming from the recent trend of highly integrated devices, which is to obtain various thin films free from heat or plasma damages by utilizing thermal CVD or PECVD-based film deposition processes.